High-frequency inductor



Oct. 13, 1953 pj N, SORENSEN 2,655,589

l HIGH-F`REQUENCY INDUCTOR i Filed June 5 1950 IN V EN TOR.

rroR/vsy Patented Oct. 13, 1953 HIGH-FREQUENCY INDUCTOR Phillips N. Sorensen, Cleveland, Ohio, assigner to The Ohio Crankshaft Company, Cleveland, Ohio, a corporation of Ohio Application June 3, 1950, Serial No. 166,036

1 Claim. 1

This invention pertains to the art of highfrequency induction heating and, more particularly, to a high-frequency inductor capable of heating extremely limited areas. Heretofore, the heating of extremely limited areas employing high-frequency induction heating has been extremely diliicult to obtain. Ordinarily, the areas have been circular in shape and there has been less actual heat in the center of the area than there has been on the outside.

The present invention contemplates an inductor construction capable of heating a limited area of a shape which is not necessarily circular and wherein the maximum amount of heat is produced at the center of the area rather than at the edges.

In accordance with the present invention, an inductor is provided which is generally U or hairpin shaped with the curve of the U adapted to be adjacent the workpiece to be heated and of limited cross-sectional area. The legs of the U extend in spaced parallel relationship away from the area to be heated and normally have a much wider cross-sectional area than the curved part. A stack of magnetic laminations having their plane parallel to the planes of the legs are disposed between the legs and extend down to overlap the curved part of the U.

An object of the invention is the provision of a new and improved inductor which is capable of heating limited areas on workpieces and which is simple in construction, electrically eilicient and easy to manufacture.

Another object of the invention is the provision of an inductor for heating limited areas of workpieces which comprises a generally U- shaped inductor including a curved portion of limited cross-sectional area adapted to be disposed in close spaced relationship to the area to be heated and a pair of spaced parallel legs of greater cross-sectional area extending away from the workpiece and magnetic laminations disposed between the legs and overlapping the curved portion adjacent the work.

The invention may be embodied in a number of different constructions and arrangements; but, for the purposes of illustrating the invention, a preferred embodiment will be described in this specification and illustrated in the attached drawing which is a part hereof, and wherein:

Figure 1 is a side elevational view of a highfrequency inductor embodying the present invention in heat-inducing relationship with a workpiece to be heated.

Figure 2 is an end elevational view of Figure 1.

Figure 3 is a detailed view of one of the laminations employed.

Referring now to the drawings wherein the preferred embodiment is shown for the purposes of illustration only and not for the purposes of limitation, Figure 1 shows a high-frequency inductor comprising a pair of terminal blocks I0, I I which are adapted to be attached to the terminal blocks not shown of a power source such as an impedance-matching transformer. A pair of iish-tail leads I2, I3 are connected at their ends to the terminal blocks II), II respectively and extend away therefrom in spaced parallel relationship and at their other ends are connected to the active heat-inducing portion of the inductor designated generally as A.

The terminal blocks ID, II may be of any desired construction. As shown, they are generally rectangular and are in slight1y-spaced insulated relationship as at I5. 'I'he right-hand side as viewed in Figure 1 has a shallow recess IB which is adapted to receive a correspondingly shaped mating portion on the terminal blocks of the power source. These blocks are also provided with a plurality of openings I'I through which mounting bolts may extend to mount the terminal blocks on the power source. These terminal blocks may be water cooled if desired.

The fish-tail leads I2, I3 are generally rectangular in cross-sectional shape and, as stated, extend away from the terminal blocks I0, I I with their sides of greatest dimensions in close spaced parallel relationship. In the embodiment shown in Figure 1, the upper leg I2 is longer than and extends beyond the lower leg I3 to the left. The inducing portion A is generally U or hairpin shaped in side elevational view and includes a pair of spaced parallel legs I9, 20 interconnected at their lower ends by a curved or arcuate portion 2I. The legs I9, 20 connect at their upper ends and at right angles to the fish-tail leads I3, I2 respectively. As shown, the legs I9, 20 at their upper ends have a width generally the same as that of the sh-tail leads I2, I3; but, at their lower ends, the legs taper to the crosssectional width of the U-shaped portion 2I. As shown, the U-shaped portion 2| is generally circular in cross section having a diameter approximately one-third the width of the legs I9, 20. This arcuate portion is generally semicircular in the side elevational view. As shown, the lower ends of the legs I9, 20 taper from their maximum width to the diameter of the portion 2I in a length corresponding approximately to two diameters of the portion 2|.

Magnetic laminations 23 are disposed between the legs I9 and 20. The plane of these laminations is parallel to the plane of the legs I9, 20. On the lower edge thereof, it has a semicircular recess formed to receive the arcuate portion 2| of the inductor. Thus, the laminations 23 at their lower edge overlap the arcuate portion 2|. Further, the outer lower corners of the laminations 23 are beveled or cut away as at 26.

Separate high-frequency currents are flowed through the inductor; for example, through the terminal block I0, the sh-tail lead |2, the leg 20, the arcuate portion 2|, the leg |9, the.shtail lead I3 and the terminal block These cur,- rents set up a high-frequency fluxield about the respective conductors. The close spacing of the terminal blocks I9, and the fish-tail leads l2, |3, however, tend to restrict and limitthe'iuxV field about these particular members. rIhe flu-x field about the arcuate portion 2| tends to thread through the workpiece w shown just below, to induce heating currents therein in an extremely limited area as shown. This flux isconcentrated by the laminations 2S, the lower edge of which it will be noted are relatively narrowed by the cut-away portion 25. Additionally, the ux about the legs I9 and 29 tends to ow into the lamina,- tions 23 and this flux also, to some extent, will show up in thelower edge of the laminations to threadY through theworkpiece. It is to be noted in Vthis respect that the laminations 23 while cut away at their lower edges are so formed in dimension belowv the cut-awayor taperingl portion of the legs |9, 2G.

It has been found in practice that an inductor constructed in accordance withthe above disclosure has proven very effective forheating spots of limited areas on metallic workpieces employing ten thousand cycles persecond alternatingfcurrent electrical energy.l The heatin the heated area is-normally uniform thereacrossand in contradistinction to other inductors for heating small areas, the temperature of. the spot is a maximum at the middle.

The invention has been described ineconnection with a preferred embodiment thereof. It will be appreciated that modications and alterations in this preferred embodiment will occur to others upon a reading and understanding of this specication. It is my intention to include all such niodications and alterations insofar as they come within the scope of the appended claim.

Having thus describedLmy invention, I claim: A highfrequency inductor comprising a pair of sh-tail leads adapted to be connected at one end to a high-frequency power source, said leads extendingfrom said power source in close-spaced insulated relationship and a generally U-shaped conductor depending from said leads and includinga pair of' slightly-spaced legs and a generally arcuate pieceinterconnecting the lower end of said legs, the upper end of said legs being each connected to one of said fish-tail leads, said arcuate; piece having a substantially lesser crosssectional area than that of said legs, said legs taperinggradually from'their greater cross-sectionalarea to the cross-,sectional area ofsad piece, magnetically-permeable,laminations dis-` posed between said legs with their planeperpene,

dicula-r to the plane. of the piece, the loweredge.

of. said laminationsbeing recessed to receive and thereby overlap. thessides4 ofrsaid arcuatepiece, the lower surface yof said .arcuate piece forming the `only Yworkpiece-facing surfaceof said induce tor.

PHILLIPS" SORENSEN.

References Cited in Vthe file. of this'patent,

UNITED STATES PATENTS Number. Name Date;

1,912,214 Northrup MaySO, 1933 2,428,985y Darmara .Sept..9, 1947 2,493,771v Marquardt etal. Jan. 10, 1950 2,493,950 Dow et al. Jan.. 1U,- 1950 2,599,086 Beckins et al June 3, 1952 FOREIGN PATENTS Number Country Date Y 70,478. Norway May 27, 1946 613,323. Great Britain Nov. 25, 1948 

